GBB model: KJW M9
Propellent: 3x 465g cans propane (Coleman, green cans), 2x cans of green gas
Failures to date: None, expect for leaking mags once in a while.
GBB model: KSC G23F FMU
Propellent: 2x 465g cans propane (Coleman, green cans). Used extended 49rd mag and G19 mag, both have stock valves.
Failures to date: Broken loading ramp after around 30 mags. Hopup rubber slightly increased in size and eventually started to fall apart close to the end of second can, not sure about the cause, I suspect propaine or silicon oil.